.b-dragging-column {
    position: absolute;
    visibility: visible;
    opacity: 50%;
    z-index: 100;
    border: black dotted 1px;
}

.b-dropzone {
    color: blue;
    background-color: yellow;
    position: absolute;
    width: 10px;
    top: 0px;
    bottom: 0px;
    left: -5px;
    visibility: visible;
}

.b-dropzone-active {
    background-color: green;
}